With the wide application of architectural glass curtain walls in China, safety accidents and problems caused by explosion and fall of architectural glass have become increasingly prominent. Frequent accidents have caused great concern at all levels of government departments. In the past, most of them were retrospective statistics of existing damage and could not predict the potential risks of existing building glass.
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Tempered glass, commonly known as "glass cancer," is an international problem that is common in glass service security but difficult to detect and "cannot be treated." In view of the bottleneck problem in the evaluation of architectural glass service safety, Bao Yibao, the chief scientist of China National Building Material Corporation’s China National Building Materials Corporation’s China National Inspection and Research Group, dared to take the lead in the world, aiming to improve its service safety and risk prediction, and to break through the architectural glass industry at home and abroad. A hundred year problem. The project he completed, "Key Technologies and Equipment and Applications for Risk Assessment and Reliability Evaluation of Architectural Glass Service," won the second prize of the 2017 National Science and Technology Progress Award.
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TheTechnological innovation allows risks to be predicted
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Bao Yiwang also believes that in order to solve this problem of risk prediction, it is necessary to clarify the mechanism and influencing factors of self-detonation, based on the inherent brittleness of glass and the characteristic of “unbreakable”. Bao Yiwang’s team research began with the search for nickel sulfide.
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Nickel sulphide impurities in the glass are only about 0.1 to 0.3 mm in diameter and are virtually invisible to the naked eye. It is extremely difficult to inspect microscopic impurities with a magnifying glass or scanner, making on-site inspection more difficult. In order to determine the nature of impurity defects, the team first collected a large number ofTempered glassThe fragment after self-explosion and the partial glass taken from the explosion source were taken for fracture analysis, and each of the self-explosive source fractures can find a tiny impurity. After analyzing the composition of a large number of impurities, Bao also found that in addition to well-known nickel sulphide, there are elements of silicon, alumina, and other impurities that have never been discovered. These impurity particles, which do not undergo phase transition, may cause incompression between the impurity particles and the glass during the heating or cooling process because the expansion coefficient is inconsistent with the glass. Such extrusion may cause the local stress of the glass to exceed a certain degree. The glass is broken by local strength and spontaneous explosion occurs. Therefore, the self-detonation of tempered glass is a brittle material mechanics and fracture mechanics caused by nickel sulfide, elemental silicon and other impurities squeeze surrounding glass and produce stress concentration. Analyze and solve problems from the perspective of mechanics. This is the strength of Bao Yiwang who is a student of solid mechanics.
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Based on the mechanics of materials and the strength model of critical failure of brittle materials, Bao Yewang established the failure criteria and self-detonation conditions for tempered glass self-explosion. It was proved that the self-explosion of tempered glass was not only due to micro-particle impurities, but also that small particles were located in the tempered glass. The tensile stress area. If the expansion coefficient of the impurity is larger than that of the glass, it will squeeze the glass during the temperature increase process, and vice versa, the interface extrusion will occur during the cooling process. Obviously, these extrusions will cause stress concentration and cause the tempered glass to blew.
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Although it is extremely difficult to detect minute impurities optically or visually, finding stress concentrations in transparent materials is an easy task. The research thinking of Bao Yiwang’s team has undergone a fundamental change from finding the stress caused by impurities in high-rise buildings’ glass self-exploding sources to detecting impurities from the source of the explosion, and revealing the correlation between the distribution of foreign particles inside the tempered glass and the surrounding stress field and discovering the self-exploding nature. The root cause is the stress concentration in the internal tensile stress region of the glass.
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Bao Yiwang's team analyzed the influence of stress particle concentration, morphology, size, and distribution location on the stress concentration in tempered glass, and obtained the influence coefficient and the classification criteria for the risk level of tempered glass self-detonation, proposed the self-detonation criterion, and developed the self-detonation of tempered glass. The source automatic detection method has developed the first transmissive and reflective photoelastic scanner at home and abroad. This technology has been formulated as a national standard GB/T 30020, which has become a key means for assessing the risk of self-detonation of tempered glass. The technology can also be applied to the investigation of the explosion source of tempered glass before the glass production line or curtain wall installation, and provides a scientific and systematic evaluation theory and a non-destructive on-line inspection method for the safe use of architectural glass and glass products.
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Bao Yewang also invented the “Dynamic Relative Method” to predict the risk of building glass fall and evaluation criteria; developed a curtain wall glass drop risk detector to automatically identify the risk level of curtain wall fall, wireless data transmission, and innovative technology is also universal. It can be extended to the service safety inspection of peripheral components such as ceramic curtain wall and stone curtain wall; and a robotic equipment for glass curtain wall security detection that can be used to detect high-rise building curtain walls is developed, solving the problem of high-altitude operation risk for high-rise building glass curtain wall inspection personnel. , Achieved the safety and intelligent detection of glass curtain walls and automated detection, and cracked the dangerous problem of the "Spider Man" high altitude on the detection of curtain walls.The
Another prominent problem in the application of architectural glass is the failure of the service of insulating glass seals, which results in the building not being energy-efficient and easily causing the glass of the outer sheet to fall off. It is more dangerous for the architectural glass to fall off the high-rise building to the ground than the self-explosion. China's hollow glass production and usage are spread all over the world, and the quality of hollow glass products and their serviceability testing are very important. The team developed a series of 10 types of durability testing equipment such as the refrigerant-free insulating glass dew tester, established a durability evaluation technology system, and built the world’s first large-scale, annual inspection of 1800 insulating glass unit durability. The testing service platform has been recognized and verified by the American Insulating Glass Certification Committee and the North American Insulating Glass Association, filling the domestic gap.
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For the hollow glass in service, Bao also reveals the relationship between its airtightness and deformation. That is, the force and deformation of the hollow layer are concentrated on the one piece of glass subjected to the force, which reduces the Hollow glass load-bearing performance increases the safety risk of cracking or falling of the outer sheet glass subjected to stress. Invented the "deflection comparison method" on-site evaluation of the effectiveness of hollow glass sealing performance failure detection technology, to achieve the on-site evaluation of the safety properties of insulating glass, for building glass safety service and disaster accident prediction provides a new technical means.
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